Fuse indicator



5. QUISLING FUSE INDICATOR April 26, 1938.

Filed Feb. 6, 1935 Patented Apr. 2c, 1938 Application February This invention relates to indicators for electric fuse cutouts of that type having an observation window therein.

Since fuse plugs were first introduced, some means has been sought whereby positive indication of the condition of the plug may be had at a glance. Various means and methods have been employed to this end, with varying degrees of satisfaction.

A thin strip of specially treated paper placed across the body of the plug above the fusible element has been tried. Upon burning out, the heat from the melting elementignites and burns this paper. If the fuse box is located in a dark place, as is usually the case, the condition of the fuse cannot be told unless an independent source of illumination is provided.

Another method employed is the use of luminescent paint applied directly to the fuse element. However, in practice, it has been found that this paint applied to the electrical current carrying element deteriorates rapidly due to the heat produced by the current passing through the element. Although the luminescence disappears, in- 25 dicating a plug apparently burned out, still the plug is actually in perfect condition, hence, this method has been found impractical. These and various other methods may, in a sense, give some indication of the condition of the fuse plug, but it is obvious that they fall short of a satisfactory solution of the problem.

The object of the present invention is to provide a fuse plug having more positive means to indicate the actual condition of the fuse at any time, and under any and all conditions.

Another object of the invention is to provide indicating means which can be applied to arm fuse plug of ordinary construction without requiring any structural changes in manufacture and with very little added cost.

With these and other objects in view, which will be seen in the description as it progresses, the invention resides in certain novel features of construction hereinafter described and claimed. It is 'of course understood that changes may be made from the embodiment shown which fall within the scope of the claims.

In the drawings:

Fig. 1 is a vertical sectional view of a fuse plug constructed in accordance with the present invention;

Y Fig. 2 is a plan view of the plug with the metal cap removed; and

Fig. 3 is a perspective view of a slightly modified form of indicator strip.

6, 1935, Serial No. 5,189

Fig. 4 is a perspective view of a further modiflcation of the indicator strip.

Fig. 5 is a perspective view of a further modification of the indicator strip.

Referring to the drawing in detail, a common 5 plug type fuse is illustrated. The fuse plug comprises the usual body I, fusible element 2, observation window 4 and metal cap 3. The body i may be formed of porcelain or other suitable insulating material.

A ribbon 5 of any suitable material, for example, paper, is placed within the fuse plug body, and held therein between the upper face of the body portion and the observation window or the metal cap. This ribbon is of a length greater than the 15 diameter of the fuse plug body I, and has its midportion bent downwardly away from the observation window 4. The ribbon is thus held with its midportion suspended below the window 4 and above the fusible element 2 in spaced relation 20 to both the window 4 and the element 2.

The upper surface of the ribbon 5 bears a suitable marking, such as the letters O. K. or the like, and is coated with a light colored, luminescent paint 6. The marking will be clearly visible 25 thru the window 4 in daylight, while at night the luminescent paint will glow softly, indicating the perfect condition of the fuse.

The upper surface of the ribbon is coated with a light-colored luminescent paint 6, which may 30 include such ingredients as the sulfide salts of zinc, barium, calcium, or strontium, singly or combined, and, if it is desired to provide a coating which is visible in a constantly dark place, radio-active substances, such as compounds of 35 mesothorium, thorium or uranium salts, may be added.

The lower surface of the ribbon is coated with a relatively poorly inflammable adhering material I, such as glue or mucilage, having suspended 40 therein a quantity of chemicals unstable to the increased temperatures produced by the blowing of the fuse, such as potassium chlorate, potassium nitrate and lead dioxide, phosphorus, sulphur and sesquisulfide of phosphorus.

Because the ribbon 5 is held suspended and away from all contact with the fuse link 2, the temperature of which varies with the load of electrical current it carries, the coating upon both sides of the ribbon will remain unchanged indefinitely, unless the fuse is overloaded. When the fuse becomes overloaded, the heat produced by the fusion of the fuse link is suflicient to cause the unstable chemical, such as potassium chlorate, to break down. The adhesive material, being of Doorly oxidizing character, is charred or carbonized and obliterates the luminescent paint or markings upon the visible surface of the ribbon. The darkening or blackening of the ribbon indicates that the fuse link has been ruptured, or, in the case of a fuse located in a dark place, the failure of the ribbon to glow indicates that the fuse link has been ruptured.

In Fig. 3, is shown a ribbon having notches I cut in its sides. These notches make the ribbon narrower in the middle, and facilitate the carbon particles reaching the top side of the ribbon.

In place of notches, it has been found equally useful to punch a hole or a plurality of holes in the ribbon, as illustrated in Fig. 4. The chemicals may be applied to the visible side of the indicator, as illustrated in Fig. 4. The indicator illustrated in Fig. 4 comprises a ribbon ll provided with a plurality of holes or perforations ll. Coating I2 contains a suspension of the chemicals unstable to heat in an adhering carbonizable material and occupies one portion of the visible portion of the ribbon l0. Coating l3 containing the luminescent material occupies another portion of the visible portion of the ribbon III.

In Fig. 5 I have illustrated a ribbon l5 provided with opposed notches l6. Coating l1 contains a suspension of the chemicals unstable to heat in an adhering carbonizable material and occupies the visible portion of ribbon I0. Coating l8 containing the luminescent material is applied over the coating ll. 4

The action of these indicators is similar to the action of the previously described indicators.

Although Fig. 1 illustrates the indicator ribbon in the preferred position in a common plug type fuse construction, the ribbon may be disposed in different positons, such as below the fuse link, in other types of transparent window fuse constructions.

Having thus described my invention, what I claim is:

1. In a fuse plug, an indicator comprising a narrow ribbon of sheet material having a discontinuous surface, a coating on a part of the visible portion of said ribbon, said coating being adapted to carbonize at the temperature of the gas produced by fusion of the fuse link, and a second coating on a part of the visible portion of said ribbon and containing a luminescent material.

2. In a fuse plug, a closed casing having a window therein, a fuse link within said casing, and an indicator within said casing between said window and said link comprising a narrow paper ribbon, at least a part of the visible portion of said ribbon being in close proximity to said link, a coating on at least a part of the visible portion of said ribbon containing a carbonizable adhesive material and an oxidizing salt, and a second coating on at least a part of the visible portion of said ribbon containing a luminescent sulfide.

3. In a fuse plug, a closed casing having a window therein, a fuse link within said casing, and an indicator within said casing between said window and said link comprising a narrow paper ribbon having a discontinuous surface. at least a part of the visible portion of said ribbon being in close proximity to said link, a coating on at least a part of the visible portion of said ribbon containing a carbonizable adhesive material and an oxidizing salt, and a second coating on at least a part of the visible portion of said ribbon containing a luminescent sulfide.

4. In a fuse plug, a closed casing having a window therein, a fuse link in said casing, and an indicator within said casing comprising a ribbon of sheet material having a discontinuous surface, at least a part of the visible portion of said ribbon being in close proximity to said link, a coating on the visible portion of said ribbon containing a carbonizable-adherent material and an oxidizing salt, and a second coating over said first coating and containing a luminescent sulfide and a radioactive salt.

5. In a fuse plug, a closed casing having a window therein, a fuse link within said casing, and an indicator within said casing comprising a ribbon having perforations in at least a part of its visible portion, said perforated part being in close proximity to said link, a coating on the visible portion of said ribbon containing a carbonizable adhesive material and an oxidizing salt dispersed therein, and a second coating ovensaid first coating and containing a luminescent sulfide.

6. In a fuse plug, a closed casing having a window therein, a fuse link within said casing, and

an indicator within said casing between said window and said link comprising a perforated rib bon, at least a part of the visible portion of said ribbon being in close proximity to said link, a

coating on the visible portion of said ribbon containing glue and potassium chlorate dispersed therein, and a second coating over said first coating and containing a luminescent sulfide and a radioactive salt.

'7. In a fuse plug, a closed casing having a window therein, a fuse link within said casing, and an indicator within said casing comprising a ribbon having opposed notches along its longitudinal edges in a visible portion of said ribbon, said notched portion being in close proximity to said link, a coating on the visible portion of said ribbon containing a carbonizable adhesive material and an oxidizing salt dispersed therein, and a second coating over said first coating and containing a luminescent sulfide.

8. In a fuse plug, a closed casing having a window therein, a fuse link within said casing, and an indicator within said casing comprising a ribbon having notches along its longitudinal edges in a visible portion of its length, at least a part of the visible portion of said ribbon being in close proximity to said link, a coating on the visible portion of said ribbon containing glue and potassium chlorate dispersed therein, and a second coating over said first coating and containing a luminescent sulfide and a radioactive salt.

SVERRE QUISLING. 

